Dosimetric evaluation of 4 different treatment modalities for curative-intent stereotactic body radiation therapy for isolated thoracic spinal metastases
To investigate the dosimetric characteristics of 4 SBRT-capable dose delivery systems.CyberKnife (CK),Helical TomoTherapy (HT), Volumetric Modulated Arc Therapy (VMAT) by Varian RapidArc (RA), and segmental step-and-shoot intensity-modulated radiation therapy (IMRT) by Elekta, on isolated thoracic spinal lesions.CK, HT.RA, and IMRT planning were performed simultaneously for 10 randomly selected patients with 6 body types and 6 body + pedicle types with isolated thoracic lesions.The prescription was set with curative intent and dose of either 33 Gy in 3 fractions (3F) or 40 Gy in 5F to cover at least 90% of the planning target volume (PTV), correspondingly.Different dosimetric indices, beam-on time, and monitor units (MUs) were evaluated to compare the advantages/disadvantages of each delivery modality.In ensuring the dose-volume constraints for cord and esophagus of the premise, CK, HT, and RA all achieved a sharp conformity index (CI) and a small penumbra volume compared to IMRT.RA achieved a CI comparable to those from CK.HT, and IMRT.CK had a heterogeneous dose distribution in the target as its radiosurgical nature with less dose uniformity inside the target.CK had the longest beam-on time and the largest MUs, followed by HT and RA.IMRT presented the shortest beam-on time and the least MUs delivery.For the body-type lesions, CK, HT, and RA satisfied the target coverage criterion in 6 cases,but the criterion was satisfied in only 3 (50%) cases with the IMRT technique.For the body + pedicle-type lesions, HT satisfied the criterion of the target coverage of ≥ 90% in 4 of the 6 cases, and reached a target coverage of 89.0% in another case.However, the criterion of the target coverage of ≥ 90% was reached in 2 cases by CK and RA, and only in 1 case by IMRT.For curative-intent SBRT of isolated thoracic spinal lesions.RA is the first choice for the body-type lesions owing to its delivery efficiency (time): the second choice is CK or HT;HT is the preferential choice for the body + pedicle-type lesions.This study suggests further clinical investigations with longer follow-up for these studied cases.
Stereotactic body radiation therapy Spinal metastases IMRT Dosimetry
Jun Yang Lin Ma Xiao-Shen Wang Wei Xu Xu Xiao-Hu Cong Shou-Ping Xu Zhong-Jian Ju Lei Du Bo-Ning Cai Jack Yang
Department of Radiation Oncology, Chinese PLA General Hospital, 28 Fuxing Road, Beijing, 100853, Chi Department of Radiation Oncology, Chinese PLA General Hospital, 28 Fuxing Road, Beijing, 100853, Chi Department of Radiation Oncology, Chinese PLA General Hospital, 28 Fuxing Road, Beijing, 100853, Chi Department of Radiation Oncology, Hainan Branch of Chinese PLA General Hospital, Haitang Bay, Sanya, Department of Radiation Oncology, Monmouth Medical Center, 300 2nd Avenue, Long Branch, NJ 07740,USA